The transforming proteins encoded by the type C virus, but clearly of host cell origin, provide potential transplantation antigens that will understandably be of direct importance in cancer. This project is focused on the production of monoclonal antibodies to these proteins that will result in the evaluation of these proteins as transplantable antigens; a determination of their presence throughout the phylogenetic scale; and a better understanding of the mechanisms of transformation and thus the means to biochemically or immunologically alter the events that lead to cell transformation.